In our eyes there is convex lens located which is formed by flexible muscles. Due to this lens, image of object formed at retina, and we can see things. Our eyes are round in shape. the outermost conversing of eye is white in front of it, transparent part cornea is situated, behind cornea dark coloured structure made of muscles is located, it is called iris. There is a small hole in iris called Pupil. Its size is controlled by the iris. In this case of more light the aperture of pupil reduces and in low light it increases. At the back of the pupil is eye lens which is located at its place with the help of muscles. The part between cornea and lens is filled with transparent fluid which is called eye fluid or Aqueous humour.
Through lens inverted image is formed on retina. Retina is a light absorber transparent membrane which has many light sensitive nerves, these are connected to brain. When these nerves send the message of the formation of image on retina to the brain, then brain converts inverted image into erect image and we see the object. The transparent fluid fill between lens and retina is called vitreous humour or fluid.
